1. Field
The invention relates to an organic light-emitting device, and more particularly, to an organic light-emitting device having improved emission efficiency and driving voltage.
2. Description of the Related Art
Organic light-emitting devices are self-emitting devices displaying images by using light generated while electrons and holes injected through an anode and a cathode, respectively, recombine in an emission layer or at the interface between a carrier transport layer and the emission layer.
In order to improve the emission efficiency of an organic light-emitting device, the balance of electrons and holes injected into the emission layer should be appropriately tuned.
An emission site may shift according to the relative number of electrons or holes injected into the emission layer. For example, if the number of holes is greater than that of electrons, the emission site in the emission layer may shift close to an electron transport layer. On the other hand, if the number of electrons is greater than that of holes, the emission site may shift in the emission layer to be close to a hole transport layer. Such a shift of the emission site affects the efficiency and lifetime characteristics of organic light-emitting devices.
A method widely used for tuning the charge balance of electrons and holes injected into the emission layer is to vary materials used to form the hole transport layer and the electron transport layer.
However, the balance of the carriers achieved with this method is not satisfactory, and thus, there is still a demand for further improvement.